PROJECTIONS TO THE NUCLEUS RAPHE DORSALIS FROM THE FOREBRAIN AND BRAIN STEM OF THE CAT / 解剖学报

ABSTRACT

Nucleus raphe dorsalis (RD) plays an important role in acupuncture analgesia. We carried on further studies on the projections of RD from the forebrain and brain stem of the cat by using a horseradish peroxidase (HRP) retrograde axonal transport method.We have observed the labeled neurons in layer Ⅴ of the proreate gyrus, area prepyriformis, nucleus lateral habenular, and hypothalamic areas (preoptic, lateral, medial and posterior areas) when HRP was injected into the rostral part of the RD. The labeled neurons were giant pyriform in shape in prereate gyrus and area prepyriformis and various shapes in the lateral habenular and hypothalamic areas.We have also found the labeled neurons in the periaqueductal gray matter, locus coeruleus, lateral and medial parabrachial nuclei, other raphe nuclei (n. centralis superior, n. raphe magnus and n. linearis intermediate) and reticular formation of the brain stem when we injected HRP into the caudal part of the RD.This present results confirm that the fibers project to the RD directly from the forebrain cortex (proreate gyrus and area prepyriformis), latral habenular nucleus hypothalamic areas, periaqueductal gray matter, locus coeruleus and other raphe nuclei. We also have found that the afferent projections to the rostral part of the RD and the caudal part of the RD had different origins, that is, the rostral part receives fibers from the forebrain and the caudal part receives fibers not only from the forebrain, but also from the brain stem. The study provided a foundation for explaining acupuncture analgesia and physiological functions of RD.